Generally, a metal wiring is used for connecting between devices or between wirings in manufacturing a semiconductor device.
A dual damascene process uses a barrier metal for preventing copper from diffusing into an interlayer dielectric layer, and uses a copper seed layer for easily coating the copper.
However, as the degree of integration of the semiconductor device is increased, the deposition of the copper seed layer is restricted so that the copper seed layer is not uniformly formed on the barrier metal.
Therefore, the copper is not coated well in a process of forming a via plug and an upper metal wiring which is the subsequent process so that a void occurs between the interlayer dielectric layer, the metal wiring, and the via plug, thereby degrading the characteristics of the semiconductor device.